To the Editor:
—I have a few comments to make concerning the paper of Drs. Bock, Moore, Dowd, and Clark, entitled "Carcinogenic Activity of Cigarette Smoke Condensate" (JAMA181:668 [Aug 25] 1962). There are several questions which have to do with the debate on the causes of cancer.When one reflects upon the broad implications of this work, he is struck by several anomalies. The mice were standard laboratory animals, and while the weight is not given, we presume it was more or less 30 gm. On the backs of these mice, from which the hair had been shaved, the equivalent of 8.3 cigarettes per day, in tar, was painted. A certain number of "skin tumors" were produced, presumably by this irritating procedure, some of which were squamous-cell carcinomas, although "the numbers of these carcinomas" were few. The amount of tar obtained from filter-cigarettes was less than from the